Determination of chloride ion by electrochemiluminescence and investigation of the mechanism

The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied.Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi-tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is5.0 ×10~(-6) mol/L and the linear calibration range extends up to 1.0 ×10~(-2) mol/L; the relative standarddeviation for 1.0 ×10~(-5) mol / L chloride is 5%. The influencing factors for chloride determination arealso discussed. The possible mechanism for the electrochemiluminescence reaction may be due to theoxidation of chloride ion in the solution to ClO~-, and the latter acts on luminol and then gives outluminescence. The method has been applied to determine the total chloride in tap water with satisfactoryresults.     

FLUORIMETRIC DETERMINATION OF TETRACYCLINE IN SERUM AND URINE

The Eu-Tetracycline(TC)-TOPO-sodium dodecyl sulfonate(SDS)system wasstudied,Experiments showed that the maximum fluorescence intensity was obtainedin the pH range of 7.5-8.7 and the concentrations of Eu~(a+),TOPO and SDS are1.0×10~(-6)mol/L,1.0×10~(-8)mol/L and 1.0×10~(-8)mol/L,respectively,This fluorescencesystem can be used for the determination of TC in serum and urine,Beer's Law isobeyed in the range of 2.0×10~(-8)mol/L=1.0×10~(-6)mol/L for the concentration of TC.The determination limit is 1.2×10~(-8)mol/L,The composition and the luminescencemechanism were discussed.     

Cholesterol oxidase biosensor based on a glassy carbon electrode modified with Nafion and methyl viologen

Cholesterol oxidase biosensor has been constructed by using bovine serum albumin and glutaraldehyde as cross linker to immobilize cholesterol oxidase and cholesterol esterase on a glassy carbon electrode modified with Nafion and methyl viologen. The biosensor has been used to determine total cholesterol in blood. The linear range of the determination is 2.5×10~7 to 1.0×10-4 mol/L. The detection limit is about 5.0×10~8 mol/L. The response time is 12 s. This biosensor has the advantage of high selectivity, sensitivity and short response time.     

Glucose Biosensor Based on Carbon/PVC-COOH/Ferrocene Composite with Covalently Immobilized Enzyme

A carbon/PVC-COOH/ferrocene composite electrode used for the determination of glucose has been prepared. The ferrocene acted as mediator was incorporated into the PVC-COOH polymer and the leakage could be prevented. The presence of carboxyl groups on the electrode surface allowed immobilizing enzyme via EDC and NHS. The ratio of PVC-COOH to graphite powder （w/w） has been studied. Amperometric determination of glucose has been performed at potential of 0.30 V vs SCE. The response time was 〈 15 s. The linear response range was of 0.1-20 mmol/L with a detection limit of 48μmol/L.     

Using PVP/SDS Complex as a Probe to Study the Inclusion Complex of β-cyclodextrin with SDS in Aqueous Solution

PVP/SDS complex was applied as a probe to study the interaction between β-cyclodextrin （β-CD） and sodium dodecyl sulfate （SDS） in aqueous solution. It has been found that a critical concentration, namely cs, exists in the relative viscosity of solution containing PVP/SDS complex versus β-CD concentration plot. As the β-CD concentration is less than cs, the relative viscosity of solution decreases sharply by adding β-CD into solution successively. On the other hand, as the β-CD concentration is greater than cs, the relative viscosity of solution increases gradually by adding β-CD into solution. The decrease of the relative viscosity of solution containing PVP/SDS in the presence of β-CD is just due to the inclusion complex of β-CD with the guest molecule SDS. And, this inclusion interaction takes down SDS from the PVP chains in solution. The ratio of the host molecule β-CD to the guest molecule SDS can be calculated from Cs. In our experiment the inclusion ratio of β-CD to SDS is 1/1. The further experimental results indicate that cs is associated with SDS but free from PVP in PVP/SDS complex. However, the inclusion ratio of β-CD to SDS has proved to be independent of either SDS or PVP in PVP/SDS complex.     

STUDY OF THE FLUORESCENCE ENHANCEMENT IN THE SYSTEM OF EUROPIUM-OR SAMAR-IUM-TERBIUM-DIBENZOYLMETHANE-CETYLTRIMETHYLAMMONIUM BROMIDE-TRITON X-100 AND ITS APPLICATION

A fluorescence enhancement phenomenon on adding terbium to the Eu or Sm-DBM-CTMAB-Triton X-100 fluorescence system was observed. The fluorescence intensity of this system was 50 times greater than that of the system without terbium at pH 9.0. The fluorescence intensity is a linear function of the concentration of europium or samarium in the range of 1.0×10~(-10)-8.0×10~(-6) mol/L and 1.0×10~(-7)-8.0×10~(-6) mol/L, respectively. The deteetion limits for them were 1.0×10~(-12) mol/L and 1.0×10~(-9) mol/L, respectively. This system was used for the determination of europium or samarium in rare earth samples with satisfactory results.     

The Electrooxidation of Tetracycline at Acetylene Black Electrode in the Presence of Sodium Dodecyl Sulfate

The electrooxidation of tetracycline (TC) at acetylene black electrode has been studied in the presence of sodium dodecyl sulfate (SDS). Tetracycline (TC) exhibited very sensitive oxidation peak in this system. The peak current was proportional to TC concentration, and the detection limit was 1.2×10-8 mol/L. The system was used to the determination of TC in Pharmaceuticals.     

Electroanalytical method for determination of shikonin based on the enhancement effect of cyclodextrin functionalized carbon nanotubes

A simple and sensitive electroanalytical method for determination of shikonin,a widely used antitumoral agent,using β-cyclodextrin-functionalized multiwalled carbon nanotubes composite modified glassy carbon electrodes(MWCNTs/β-CD/GCE) was presented.CDs are water-soluble and environmentally friendly and can improve the dispersibility of MWCNTs/β-CD functional materials,which was confirmed by SEM.The electrochemical behaviors of shikonin on different electrodes were investigated by cyclic voltammetry(CV) and differential pulse voltammograms(DPVs).The results demonstrated that the redox peak currents of shikonin obtained at MWCNTs/β-CD/GCE were much higher than those at theβ-CD/GCE and MWCNTs/GCE,which can be attributed to the combination of the excellent electrocatalytic properties of MWCNTs and the molecular recognition ability of β-CD.At MWCNTs/β-CD/GCE,the response current exhibits a linear range from 5.0 nmol/L to 10.0 μmol/L with a detection limit of 1.0 nmol/L(S/N = 3).As a practical application,the proposed method was applied to quantitatively determine shikoninin urine samples with satisfying results.     

Gold nanoparticles-enhanced bisphenol A electrochemical biosensor based on tyrosinase immobilized onto self-assembled monolayers-modified gold electrode

A novel electrochemical sensor based on the immobilization of tyrosinase(tyr) onto gold nanoparticles(nano-Au) and thioctic acid amide(T-NH2) self-assembled monolayers(SAMs)-modified gold electrode has been developed for the determination of bisphenol A(BPA).It was found that the nano-Au could significantly enhance the electrochemical response of tyr/nano-Au/T-NH2/Au electrode to BPA,and the enhancement effect of nano-Au on the current response was also related to the enzyme.The results indicated that the biosensor could be used as a detector for BPA determination with a linear range from3.99 ×10-7mol/L to 2.34 ×10-4mol/L and a detection limit of 1.33×10-7mol/L.In addition,this biosensor showed good reproducibility.     

Aversatile β-cyclodextrin functionalized silver nanoparticle monolayer for capture of methyl orange from complex wastewater

The toxic organic dye contaminants in wastewater are extremely harmful to the ecosystem.Surface enhanced Raman scattering(SERS) is a technique with high sensitivity and chemical specificity which fulfills the requirements for monitoring dye contaminants in wastewater.However,as one of the common dye contaminants,methyl orange(MO) has very weak affinity to metallic surfaces and is difficult to be detected by SERS at low concentrations.Therefore,a new type of SERS substrate with Ag nanoparticle monolayer functionalized by mono-6-deoxy-6-thio-β-cyclodextrin(β-CD-SH) was prepared to efficiently capture and detect MO in wastewater with a limit of detection of 5×10^-7 mol/L.The hydrophobic cavity of β-CD is responsible for the efficient trap and enrichment of MO on the Ag NPs surface,achieving a strong SERS signal of MO at low concentrations and at different pH values.This study provides new insight into designing a well-performed adsorbent for the capture and detection of organic contaminants.     

Study on the Deactivation Kinetics of Pd（PPh3）2Cl2 in the Monocarbonylation of Benzyl Chloride

The deactivation kinetics of Pd(PPh3)2Cl2 in the monocarbonylation of benzyl chloride to synthesize phenylacetic acid is studied in this paper. Solid 1-(2-pyridylazo)-2-naphthol (PAN) is used as the colouring agent, and the concentration of Pd(PPh3)2Cl2 in the system is measured through absorptiometry. The result shows that the optimum condition of the chromogenic reaction between Pd2+ and PAN is: 0.5 ml of 0.04% PAN added to 10 ml of Pd2+ solution (1.0×10-6-2.0×10-5 mol/L), and heated in a constant temperature water bath at 40℃ for about 30 min, with pH of the solution being about 3.0. The molar coefficient of absorption is 1.384×104 L/(mol·cm); the orders of the hydrolytic reaction to the concentration of Pd(PPh3)2Cl2, PPh3, phenylacetic acid and NaOH are 0.5, minus 0.8, 2 and 1.2, respectively. The activation energy (E) of the hydrolytic reaction is 75.59 kJ/mol, and the pre-exponential factor is 1.68×1012.     

Monitoring of Methyldopa by Fast Fourier Transform Continuous Cyclic Voltammetry at Gold Microelectrode

A continuous cyclic voltammetric study of methyldopa at gold micro electrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorpted at 400 mV, giving rise to change in the current of well-defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest one of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal-to-noise ratio has significantly increased by application of discrete Fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10－7—1.0×10－11 mol•L－1 (r＝0.9975) with a limit of detection and quantitation 0.004 nmol•L－1 and 0.03 nmol•L－1, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay methyldopa in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the methyldopa were considered.     

Study on the Supramolecular Interaction of β-Cyclodextrin with Gemfibrozil by Spectrofluorimetry and Its Analytical Application

The supramolecular interaction of gemfibrozil with β-cyclodextrin （β-CD） was studied by spectrofluorimetry. The mechanism of the inclusion was discussed by spectrofluoremetry, infrared spectrum and ^1H NMR spectrum. The results showed that a 1 ： 1 （β-CD ： gemfibrozil） complex was formed with an apparent association constant of 3.844 × 10^3 L·mol^-1. Based on the enhancement of the fluorescent intensity of gemfibrozil, a spectrofluorimetric method for the determination of gemfibrozil in bulk aqueous solution in the presence of β-CD was developed. The linear range was 3.30 ng·mL^- 1 -6.00 ug·mL^-1 with the detection limit of 0.980 ng·mL^-1. There was no interference from the excipients normally used in tablet composition and the serum main compositions. The proposed method was then successfully applied to the determination of gemfibrozil in capsules and serum.     

Simultaneous determination of dihydroxybenzene isomers utilizing a thiadiazole film electrode

The present study reports a sensitive electro-analytical method for the simultaneous determination of dihydroxybenzene isomers by using a thiadiazole film electrode, which was readily prepared by electropolymerization of 2,5-dimercapto-1,3,4-thiadiazole on a glassy carbon electrode with cyclic voltammetry. The functionalized electrode has a distinguishable and sensitive response to dihydroxybenzene isomers. Under the optimized conditions, the linear stripping peak currents showed good linear relationships with hydroquinone, catechol and resorcinol at concentration ranges 0.50-120, 0.50-110 and 1.00-110 μmol/L, and the detection limits are 0.1, 0.1 and 0.3 μmol/L, respectively. The proposed method is applicable to the simultaneous determination of dihydroxybenzene isomers in real samples with the relative standard deviations of less than 5.7% and the recovery rates of 95.6%-106%. The constructed electrode is characterized by simple preparation, good selectivity, and high sensitivity advantages.     

Photoacoustic Spectrometry Investigation and Determination of Rare Earth Ions Ho3+ and Nd3+ in a Solution

A home-made high sensitive photoacoustic transducer was used to determine the photoacoustic signal in a solution. The photoacoustic spectra of Ho in different solvents were measured and comparedwith its absorption spectrum. The affection factors of photoacousticsensitivity are discussed. The trivalent rare earth ions Ho3+ and Nd3+in an aqueous acetonitrile solution were determined. The detection limit is 5×10-8 mol/L for Ho3+ and 1.0 ×10-7 mol/L for Nd3+, and corresponds to the absorbance of 1.5×10 and 6.3×10-7.respectively.     

A bismuth(Ⅲ) PVC membrane ion selective electrode based on5-(3,4,5-trimethoxyphenyl)-4-amino-1,2,4-triazole-3-thiol

The construction,performance characteristics and application of a new bismuth(Ⅲ) PVC membrane electrode based on 5-(3,4,5-trimethoxyphenyl)-4-amino-1,2,4-triazole-3-thiol are reported in this paper.The designed sensor exhibited a Nernstian response for Bi~(3+) ion ranging from 5.0×10~(-7) mol/L to1.0×10~(-2) mol/L with a slope of 19.8 mV/decade.The operational pH range of the sensor is 3.0-6.0.The electrode shows a response time of 6 s and can be used for at least five weeks without any considerable divergence in potentials.It exhibits very good selectivity relative to a wide variety of alkali,alkaline earth,transition and heavy metal ions.The proposed electrode could be used as an indicator electrode in potentiometric titration of Bi~(3+) ions with EDTA and in the determination of Bi~(3+) content in stomach medicine.     

Frequency characteristic of series piezoelectric sensor and application to the determination of water in organic solvents

Theoretical consideration was proposed for the frequency response of a series piezoelectric sensor to the properties of liquid and verified experimentally. This kind of sensor has sensitive and selective frequency response to the permittivity and specific conductivity of solution with excellent stability, and was applied to the determination of micro-content of water in organic solvents. The detection limit is 0.01 g/L in dioxane.     

Synthesis of difluoromethylated benzylborons via rhodium(Ⅰ)-catalyzed fluorine-retainable hydroboration of gem-difluoroalkenes

The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ration of arylgem-difluoroalkenes leading to a series of α-difluoromethylated benzylborons.The use of cationic rhodium catalyst and a biphosphine ligand with large bite angle was crucial for reactivity by offering good regioselectivity and diminishing the undesired β-F elimination.Preliminary derivatizations of the products were conducted to showcase the utility of this protocol.     

Studies on the Electrochemical Behavior of Bleomycin at a Co/GC Ion Implantation Modified Electrode and Its Application

In a 0. 10 mol/L HAc-NaAc buffer solution (pH = 4. 59), a sensitive reduction peak of bleomycin was observed by linear sweep voltammetry at a Co/GC ion implantation modified electrode. The peak potential was-0. 73 V(iw. SCE). The peak current was proportional to the concentration of bleomycin over the range of 5.0 × 10-8-1.0× 10-6 and 1.0× 10-6-1. 0 × 10-5 mol/L with a detection limit of 2.0 × 10-8 mol/L. The electrochemical behavior of the reduction peak of bleomycin at the Co/GC modified electrode was studied by linear sweep and cyclic voltammetry and applied to the determination of bleomycin in urine. This method is simple, rapid and reliable. The reduction process is quasi-reversible. The experiments of AES and XPS showed that Co was surely implanted into the surface of GCE and the depth distribution of Co was in good agreement with Gooses normal distribution; the implanted Co at GCE improved the electrocatalytic activity.     

Multianalyte Biosensor for Simultaneous Determination of Glucose and Galactose Based on Micromachined Chamber-type Electrodes

An amperometric multianalyte biosensor for the simultaneous determination of glucose and galactose was developed based on chamber-type electrodes, which were fabricated by micromachining technology. The dual cham-ber-type enzyme electrode with glucose and galactose sensor elements was integrated onto one microchip. The experimental parameters of this biosensor were optimized. The biosensor exhibited a linearity of up to 4.0 mol/L for glucose and 4.5 mol/L for galactose, and the response time was about 30 s for glucose and 40 s for galactose. No cross-talking behavior was investigated in the course of simultaneous measurement of the two analytes. Interference from electroactive species, such as ascorbic acid and uric acid, was minimized due to the permselectivity of Nation film. In addition, the biosensor displayed a storage stability of longer than one month.